I moved to the US on January 3rd 2014, and stayed there for most of the year (~273 days). I'm still living in the US. I seem to meet the substantial presence test (right?), but for some reason after calling the IRS, they told me I should file under Dual Status because I was considered a non-resident for Jan 1 and 2 2014.
Is the IRS person correct?
Yes, they're correct.
From the IRC Sec. 7701(b)(2)(A)(iii):
Residency starting date for individuals meeting substantial presence test In the case of an individual who meets the substantial presence test of paragraph (3) with respect to any calendar year, the residency starting date shall be the first day during such calendar year on which the individual is present in the United States.
You can still claim deductions, just not the standard deduction.
They are correct assuming that you were nonresident for all of 2013. See First Year of Residency.
However, if you're married, then you have the option to become a resident alien for all of 2014 and file jointly with your spouse. To do this, you would use either Choosing Resident Alien Status (if your spouse is resident or dual status for 2014) or Nonresident Spouse Treated as Resident (if your spouse is nonresident for 2014).
